| 1. |
- Chakraborty, S., et al.
(författare)
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Symbolic trajectory evaluation for word-level verification: theory and implementation
- 2017
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Ingår i: Formal Methods in System Design. - : Springer Science and Business Media LLC. - 1572-8102 .- 0925-9856. ; 50:2-3, s. 317-352
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Tidskriftsartikel (refereegranskat)abstract
- Symbolic trajectory evaluation (STE) is a model checking technique that has been successfully used to verify many industrial designs. Existing implementations of STE reason at the level of bits, allowing signals in a circuit to take values from a lattice comprised of three elements: 0, 1, and X. This limits the amount of abstraction that can be achieved, and presents limitations to scaling STE to even larger designs. The main contribution of this paper is to show how much more abstract lattices can be derived automatically from register-transfer level descriptions, and how a model checker for the general theory of STE instantiated with such abstract lattices can be implemented in practice. We discuss several implementation issues, including how word-level circuits can be symbolically simulated using a new encoding for words that allows representing X values of sub-words succinctly. This gives us the first practical word-level STE engine, called STEWord. Experiments on a set of designs similar to those used in industry show that STEWord scales better than bit-level STE, as well as word-level bounded model checking.
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| 2. |
- Isheden, Christian, et al.
(författare)
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Formation of Ni mono-germanosilicide on heavily B-doped epitaxial SiGe for ultra-shallow source/drain contacts
- 2003
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Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172 .- 1946-4274. ; 745, s. 117-122
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Tidskriftsartikel (refereegranskat)abstract
- The formation of Ni germanosilicides during solid-state interaction between Ni and heavily B-doped strained epitaxial Si1-xGex films with x=0.18, 0.32 and 0.37 is studied. No NiSi2 is found in these samples even after annealing at 850 degreesC, which can be compared to the formation of NiSi2 at 750 T on Si(I 00). Resistance and diffraction studies for the Si0.82Ge0.18 sample indicate that NiSi0.82Ge0.18 forms and the NiSi0.82Ge0.18/Si0.82Ge0.18 structure is stable from 400 to 700 degreesC. For the NiSi1-uGeu formed in all Si1-xGex samples, where u can be different from x, a strong film texturing is observed. When the Ge fraction is increased from 18 at.% to 32-37 at.%, the morphological stability of the film is degraded and a substantial increase in sheet resistance occurs already at 600 degreesC. The contact resistivity for the NiSi0.8Ge0.2/Si0.8Ge0.2 interface formed at 550 T is determined as 1.2x10(-7) Omegacm(2), which satisfies the ITRS contact resistivity requirement for the 70 nm technology node.
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| 3. |
- Jarmar, T., et al.
(författare)
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Germanium-induced texture and preferential orientation of NiSi1-xGex layers on Si1-xGex
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:23, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- NiSi1-xGex films on compressively strained as well as relaxed undoped Si1-xGex epitaxially grown substrates with x=0.06-0.30 on Si(001) wafers have been studied with respect to the relative orientation of film and substrate after annealing at temperatures in the range 400-850 degreesC. Using x-ray diffraction, transmission electron microscopy, and pole-figure measurements, it was found that only the monogermanosilicide phase formed above 450 degreesC and was the only phase still at 850 degreesC. New information regarding the effects of Ge on the silicidation of Ni was also found. Thus, the preferred plane parallel to the surface is (013). Compared to NiSi, Ge suppresses the development of the other planes parallel to the surface except (013). Within this plane, the orientations of the grains pile up in such a way that the configuration NiSi1-xGex[100]//Si1-xGex[100] is avoided, which in the pole-figures leads to broad peaks in-between the substrate [100] and [010]. In addition, peaks indicating the epitaxial alignment NiSi0.8Ge0.2(+/-21-1) or (+/-2-11)//Si0.8Ge0.2(+/-2+/-20) coupled with NiSi0.8Ge0.2(+/-100)approximate to//Si0.8Ge0.2(+/-100) or (0+/-10) were found. Fine structure in the broad peaks is found to be due to lateral epitaxial alignments between grains along their common grain boundary. Based on the nonexistence of NiGe2, the observations are interpreted in terms of Ge preventing the formation of certain Ni-Ge bonds at the interface between NiSi1-xGex and the Si1-xGex substrate.
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| 5. |
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| 6. |
- Jarmar, T., et al.
(författare)
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Morphological and phase stability of nickel-germanosilicide on Si1-xGex under thermal stress
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:12, s. 7193-7199
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Tidskriftsartikel (refereegranskat)abstract
- Continuous and uniform Ni(Si,Ge) layers are formed on polycrystalline Si and Si0.42Ge0.58 substrate films at 500 degreesC by rapid thermal processing. The germanosilicide is identified as NiSi0.42Ge0.58, i.e., with the same Si-to-Ge ratio as in the substrate. The NiSi0.42Ge0.58 layer has agglomerated at 600 degrees C. This is accompanied by a diffusion of Ge out from the germanosilicide grains and the growth of a Ge-rich SiGe region in their close vicinity. These changes cause a slight variation in the atomic composition of Ni(Si,Ge) detectable for individual grains by means of energy dispersive spectroscopy. Above 600 degreesC, substantial outdiffusion of Ge from the Ni(Si,Ge) grains occurs concurrently with the migration of the grains into the substrate film away from the surface area leaving a Ge-rich SiGe region behind. These observations can be understood with reference to calculated Ni-Si-Ge ternary phase diagrams with and without the inclusion of NiSi2. When Ge is present, the Ni-based self-aligned silicide process presents a robust technique with respect to device applications.
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| 7. |
- Olsen, Sarah H., et al.
(författare)
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Control of self-heating in thin virtual substrate strained Si MOSFETs
- 2006
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Ingår i: IEEE Transactions on Electron Devices. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9383 .- 1557-9646. ; 53:9, s. 2296-2305
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the first results and analysis of strained Si n-channel MOSFETs fabricated on thin SiGe virtual substrates. Significant improvements in electrical performance are demonstrated compared with Si control devices. The impact of SiGe device self-heating is compared for strained Si MOSFETs fabricated on thin and thick virtual substrates. This paper demonstrates that by using high-quality thin virtual substrates,,the compromised performance enhancements commonly observed in short-gate-length MOSFETs and high-bias conditions due to self-heating in conventional thick virtual substrate devices are eradicated. The devices were fabricated with a 2.8-nm gate oxide and included NiSi to reduce the parasitic series resistance. The strained layers grown on the novel substrates comprising 20% Ge did not relax during fabrication. Good ON-state performance, OFF-state performance, and cross-wafer uniformity are demonstrated. The results show that thin virtual substrates have the potential to circumvent the major issues associated with conventional virtual substrate technology. A promising solution for realizing high-performance strained Si devices suitable for a wide range of applications is thus presented.
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| 8. |
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| 9. |
- Pope, Jeremy, 1991, et al.
(författare)
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Bifrodie;st: Creating Hardware with Building Blocks
- 2023
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Ingår i: Forum on Specification and Design Languages. - 1636-9874. ; 2023-September
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Konferensbidrag (refereegranskat)abstract
- Domain-specific hardware design has become increasingly attractive as single-Thread performance improvement has drastically slowed down. At the same time, it is clear that traditional hardware design approaches are difficult and error-prone. In this paper we describe a hardware design language, Bifrodie;st, aimed at allowing clear, correct, and modular specification of hardware. Bifrodie;st is tightly integrated into the Thor system, and thus a design in Bifrodie;st can be refined in a correctness-preserving way to a realistic hardware implementation. This paper gives both syntax and semantics of the language, highlights important design decisions, and illustrates its use in several projects. copy; 2023 IEEE.
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| 10. |
- Pope, Jeremy, 1991, et al.
(författare)
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Cephalopode: A custom processor aimed at functional language execution for IoT devices.
- 2020
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Ingår i: 2020 18th ACM-IEEE International Conference on Formal Methods and Models for System Design, MEMOCODE 2020.
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Konferensbidrag (refereegranskat)abstract
- The Internet of Things (IoT) conceives a future where "things"are interconnected by means of suitable information and communication technologies. Unfortunately, recent events have demonstrated the high vulnerability of IoT. One of the main reasons for this is the use of low-level programming languages. The Octopi project is developing technologies to easily and securely program IoT devices by the use of functional high-level languages. Unfortunately, a traditional implementation of a modern functional language that runs on traditional hardware is very resource demanding. So resource demanding that few, if any, IoT devices can run them.In the Cephalopode project (which is a subproject of Octopi) we are exploring the implementation of a very low power hardware device directly aimed at running a high-level functional language. By integrating many resource-heavy tasks into dedicated hardware, we aim at creating an execution engine for IoT devices that will allow secure programming.
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